1. Field of the Invention
The present invention relates to a vehicle occupant restraint system, and in particular, to a vehicle occupant restraint system provided with an electric actuator.
2. Description of Related Technology
Conventionally, when it is determined that there is a possibility of vehicle collision, the motor (electric actuator) is positively rotated to enable transmission of the motor drive system, the seatbelt is wound around a spindle to lightly restrain the occupant, and, when it is subsequently determined that there is no longer a possibility of collision, the motor is reversely rotated to disable the transmission of the motor drive system and return it to its original state. This is a three-point seatbelt retractor which increases the restraint with a pretensioner upon a collision, and thereby reliably protects the occupant.
As this kind of seatbelt retractor, known is a seatbelt device which transmits the motive power of the motor to the spindle via the gear train with a torque limiter mechanism built therein and the clutch mechanism, and thereby winds the seatbelt (for instance, refer to Patent Document 1 identified below). In addition, with this clutch mechanism, the connection/disconnection between the motor and the spindle can be reversibly switched when the pretensioner is not actuated, and the motor and the spindle are irreversibly disconnected when the pretensioner is actuated.
Moreover, also known is a seatbelt retractor, wherein the power transmission mechanism which transmits motive power from the motor to the spindle comprises a low reduction ratio reduction mechanism configured from a gear train, and a high reduction ratio reduction mechanism configured from a planetary gear, and the seatbelt retractor is actuated in a low reduction ratio power transmission mode by the low reduction ratio reduction mechanism when the tensile force of the seatbelt is a predetermined value or less, and in a high reduction ratio power transmission mode by the high reduction ratio reduction mechanism when the tensile force of the seatbelt is greater than a predetermined value so as to simultaneously achieve the swift winding of the seatbelt, and the winding of the seatbelt at a high torque, whereby a pretensioner using reactant gas is no longer required (for instance, refer to Patent Documents 2 and 3 identified below).
Patent Document 1: Japanese Translation of PCT Application No. 2006-123750
Patent Document 2: Japanese Patent Application Publication No. 2005-29014
Patent Document 3: Japanese Patent Application Publication No. 2006-103453
Meanwhile, when a power transmission mechanism that configures the motor drive system of Patent Document 1 includes a clutch mechanism, the actual winding of the seatbelt does not start until the motor is rotated a predetermined angle or more from when the actuation of the motor is started due to the time that is required for the clutch mechanism to become a connected state or the gaps between the respective components, and there is a problem in that much time is required from when the actuation of the motor is started to when the actual winding of the seatbelt is started. Thus, there are demands for swifter and more reliable actuation of a seatbelt retractor.